Apparatus for making contactless measurements of the thickness of an object made of transparent material

An apparatus for making a contactless measurement of a spacing between reflecting forward and rearward boundary surfaces and especially for determining the thickness of a measurement object made of transparent material and defining said reflecting forward and rearward boundary surfaces, the apparatus comprising:

• first and second radiation sources for generating said first and second beams;
• first and second beam deflecting devices made of transparent material;
• first and second position-resolving detectors mounted adjacent corresponding ones of said beam deflecting devices;
• said first deflecting device defining a first surface facing toward said first radiation source and said second deflecting device defining a second surface facing toward said second radiation source;
• said first surface conjointly defining a beam entry and a splitting surface causing said first beam to split at said first surface to form a first component beam that enters said first deflecting device at said first surface and is directed along a first beam path toward the measurement object;
• said second surface conjointly defining a beam entry and a splitting surface causing said second beam to split at said second surface to form a second component beam that enters said second deflecting device at said second surface and is directed along a second beam path toward the measurement object;
• said first and second deflecting devices being positioned relative to each other so as to cause said first and second component beams to define first and second beam paths which run toward each other and impinge inclined at said forward boundary surface whereat:
• (a) radiation of said first component beam is reflected at both of the boundary surfaces toward and into said second deflecting device along and in the direction of said second component beam path up to said second surface whereat said radiation of said first component beam is decoupled from said second component beam and reflected toward said second position-resolving detector;
• and,
• (b) radiation of said second component beam is reflected at both of the boundary surfaces toward and into said first deflecting device along and in the direction of said first beam path up to said first surface whereat said radiation of said second component beam is decoupled from said first component beam and reflected toward said first position-resolving detector.